Field
Aspects of the present invention generally relate to an image reading apparatus that conveys a document and generates and processes image data.
Description of the Related Art
An image reading apparatus having a document feeding-reading function for reading a document placed on a document conveyance unit (auto document feeder (ADF)) is known.
It is known that such an image reading apparatus is configured to make the user set in advance the size of a document to be read, and read the document placed on a document stacking unit in a standard size set by the user. As a method for previously detecting the size of a document placed on the document stacking unit of the ADF by using a document detection sensor, a method for automatically setting the size of a document to be read (Japanese Patent Application Laid-Open No. 2000-314991) is known. Japanese Patent Application Laid-Open No. 2000-314991 discusses a mode (normal mode) of reading a document in a standard size detected by the document detection sensor.
Calculating the length of a document in a conveyance direction in the middle of a document conveyance path has also been known (Japanese Patent Application Laid-Open No. 2002-060089).
If the size of a document to be read is automatically detected by the document detection sensor to read a document of standard size, the size of the actual document may differ from the size of the document detected by the document detection sensor. Specifically, if a document in a curled state (hereinafter, a curled document) or a document in a folded state (hereinafter, a Z-folded document) is placed on the document stacking unit, the document detection sensor can falsely detect the size of the document. A possible reason is that when the sensor in used is configured to detect the presence or absence of a document, if the curled or folded portion of the document floats above the document stacking unit, the sensor may fail to detect that portion.
If a plurality of documents of different sizes is placed on the document stacking unit, the document detection sensor may detect the document size of a document different from one about to be read. The reason is that if a plurality of documents of different sizes is stacked and placed and the sensor for detecting the presence or absence of a document is used to detect the document size, the detection result depends on the maximum document size.
False size detection on the document stacking unit can be determined based on the length of the document in the conveyance direction in the middle of the document conveyance path. For example, if a control unit determines that the result of the document detection sensor is different from the result calculated in the middle of the conveyance path, the control unit can cancel the read job and notify an error message.
If the document detection sensor falsely detects a size smaller than that of the actual document, image data is generated in which a part of the actual document is missing. Accordingly, error processing needs to be performed when a false detection occurs. On the other hand, if the document detection sensor falsely detects a size larger than the document size, the reading area is larger than the actual document size and the image data including the entire image on the document can be generated. Nevertheless, the error processing is conventionally performed every time a false size detection occurs. The user's convenience has been rather impaired since the job is cancelled even if the document detection sensor falsely detects a size greater than the document size.